The last quarter of a century has seen remarkable advances in the field of nano-particles, including carbon or carbon containing nanoparticles. Reference is made to hitherto undiscovered allotropes of carbon such as various fullerenes, including carbon nanotubes (CNTs). Reference is also made to graphene, which is a single layer of graphite, and also to graphene containing nanoparticles such as graphene nano platelets (GNPs). There is a huge amount of interest in graphene and graphite-based materials in view of their remarkable electrical, thermal, mechanical and physical properties. Already, a huge amount of effort and expense has been put into the development of these materials and the exploitation of the remarkable properties. However, there are problems in manufacturing CNTs and graphene based materials, particularly for large-scale industrial applications. Furthermore, there are problems in handling these materials. The problems have so far been a barrier to commercial-level exploitation of materials such as CNTs and graphene based materials.
More specifically, it is well-known to synthesise CNTs and graphene containing materials such as GNP at low temperature using methods such as arc discharge and Catalytic Chemical Vapour Deposition (CCVD). It is also known to use acid intercalation of graphites, and to produce graphene from graphene oxide by thermal annealing, chemical, photocatalytic and plasma reduction. All of these methods, to a greater or lesser extent, offer a potential for relatively large-scale production. However, all of these methods result in an abundance of defects and disorder in the CNT and graphene containing products which are introduced by processes such as oxidation and exfoliation. Once synthesised, these problems are further compounded as conventional manipulation of graphenes and CNTs into a practical, useful material involves harsh, intensive mechanical and chemical processing. This further processing again degrades the surface of the material by generating additional defect sites. This occurrence is a common event irrespective of whether the materials produced are in sheet form, tubular (such as CNTs), or in other structural forms such as bucky balls, nano onions, or other graphene containing structures. The defects and disorders introduced by these prior art techniques severely degrade the materials' usefulness in any of the wide range of end applications which might be envisaged, such as use as a material enhancing filler, or as a facilitating component within any one of the wide range of devices for sensing, catalysis, or other high value end applications.
Additionally, many of the particles, such as CNTs, are difficult to handle and to produce in an acceptable state owing to their very pronounced tendency to aggregate or agglomerate under the influence of van der Waals' forces. The inherently high “specific surface area” of nanoparticles, together with (for structures such as CNTs) a high aspect ratio, exacerbates this tendency.
It is known to treat and/or produce nanoparticles such as CNTs and graphene platelets using a glow discharge plasma. Apparatus suitable to perform such treatments are disclosed in International Publications WO2010/142953 and WO2012/076853, the entire contents of both of which are herein incorporated by reference. However, WO2010/142953 and WO2012/076853 are not believed to be compatible with optimised large scale production. More specifically, it would be highly desirable to provide improvements in large scale production parameters such as processing efficiency and throughput. Furthermore, it would be highly desirable to provide an improved apparatus which can produce nanoparticles having better properties and characteristics, such as highly crystalline nanoparticles and nanoparticles having a reduced tendency to aggregate or agglomerate. Yet further, it would be highly desirable to provide apparatus and methods which enable novel and improved particles, including nanoparticles, to be produced.